Pneumatic control



Sept. 1, 1959 R. D. COWHERD PNEUMATIC CONTROL Filed June 5. 1957INVENTOR. ROBERT D. COM HERD B) ATTORNEYS This invention relates topneumatic controls and par- Zticularly to a pneumatic control valve orair switch which .may be magnetically actuated and is characterized by aconstruction which permits easy adaptation of the device for use aseither a normally closed or normally open air .switch.

in the field of instrumentation, and in particular in the fabrication ofpneumatic control systems, both normally closed and normally open airswitches are frequently used, both types of switches often being used inthe .same system. With these conditions in mind, the desirability of anair switch which can be easily modified to .provide either normallyclosed or normally open opera- .tion is apparent. Further, sincesensitive measuring or -.sensing devices normally have very little poweror energy .available for the actuation of their accompanying control.devices, it is desirable that the controlling member be (capable ofbeing moved between its controlling positions with a minimum couplingforce between the sensing element and the controller. Opposing thisrequirement is the necessity for providing a positive re-setting forcefor the controlling member so as to insure a clean, snap- .actingoperation of the air switch.

The present invention provides an air switch in which :a U-shapedcontrolling member cooperates with a pres- ;sure nozzle to perform theswitching function, and in which a re-setting orifice provides a forcefor positively resetting the controlling member when the switch isdeactuated. The construction is characterized by the fact that by merelyrotating the control body 180 with reference to the U-shaped controllingmember, the air switch may be transformed from a normally open switch toa normally closed switch, or vice versa.

A further object of the present invention is to provide a magneticallyactuated air switch of the type referred to above in which a permeablelink, or flag, carried at .the extremities of the U-shaped controllingmember, may be readily varied either in horizontal or vertical dimensionto thereby provide a flexibility in the operating differential of theapparatus.

A further object of the present invention is to provide an air switch ofthe type referred to above in which the controlling nozzle is adjustablewith relation to the cooperating surface of the controlling member.

These and other objects will become apparent as the description proceedswith reference to the accompanying drawings in which:

Fig. 1 is a side sectional view of an air switch embodying the presentinvention.

Fig. 2 is a View of the air switch taken generally along the line 2-2 ofFig. 1.

Fig. 3 is a view similar to Fig. 1 but showing the control body rotated180 to provide a normally closed switch.

Fig. 4 is a fragmentary, enlarged view of a modified form of a portionof the apparatus shown in Fig. 1.

Fig. 5 is an enlarged fragmentary view of a further United States Patentmodified form of a portion of the apparatus shown in Fig. 1.

Referring initially to Figs. 1 and'2, there is shown at 1t a controlbody having therein a central, T-shaped pressure chamber 11. Thepressure chamber is connected to an inlet tube 12 through a restrictedorifice 13, and, at a point spaced laterally from the orifice 13 hasunrestricted communication with an outlet tube 14. At its upper end thecontrol body carries a bracket 15 having upwardly extending legs. Thebracket is fixedly held in relation to the control body by means of anozzle member 17 which is threaded through the base of the bracket andinto the control body. A spring washer 18 is interposed between theunderside of the nozzle head and the bracket. A nozzle passage 19extends centrally through the nozzle member and communicates with thepressure chamber 11. Displaced laterally somewhat from the axis of thenozzle passage the bracket 15 carries a stationary pin 21 upon which isjournaled for rotation a sleeve 22. The sleeve 22 carries rigidlysecured thereto a U-shaped controlling member 23, having a horizontalportion 24 and depending legs 26 and 27. Controlling member 23 is thusadapted to be pivotally moved about the pin 21. Members or plates 28 and29 are carried at the ends of the legs 26 and 27, respectively, theplates being preferably formed of high permeability material in contrastto the controlling member 23 which is preferably formed of anon-permeable material such as brass. A controlling magnet 31 is shownschematically and is conventionally adapted to be moved toward and awayfrom the leg 26 by a conventional sensing device operated in response toa change in the condition which is to determine the operation of anexternal pneumatic component attached to the lead-off tube 14 as is wellknown in the art. A re-setting orifice 32 extends through one side ofthe control body communicating with the interior of the tube 12, thekinetic energy of the air issuing from the resetting orifice acting uponthe leg 27 to oppose the force exerted by the magnet 31.

The operation of the pressure switch will now be described withreference to Fig. 1. The inlet tube 12 may be assumed to be connected toa suitable source of pneu matic control pressure which may be of theorder of 25 lbs. per square inch. The lead-off or outlet tube 14 may beassumed to communicate with an external pneumatic component, theoperation of which is to be controlled. In Fig. 1 the air switch isshown in its actuated position, that is, the magnet 31 has beenpositioned closely adjacent the permeable member 28 and the attractiveforce exerted thereon has moved the controlling member 23 from itsbroken line position to its solid line position, thereby closing thenozzle passage 19. This movement has been opposed by the kinetic energyof the air issuing from the re-setting orifice 32 and by the pressureexerted against the member 23 at the nozzle 17. When the externalsensing device (not shown) moves the magnet away from infiuencingrelation to the permeable member 28, the force exerted on the leg 27 atthe re-setting orifice will snap the controlling member 23 into itsbroken line position of Fig. 1, thereby uncovering the orifice passage19. Since the capacity of the passage 19 is considerably greater thanthe capacity of the orifice 13, with the passage 19 uncovered thepressure within the chamber 11 will immediately decrease, lowering thepressure in the tube 14 and thereby de-actuating the remote pneumaticcomponent connected to the tube 14. When the magnet 31 is again movedinto attracting relation with the permeable. member 28, the controllingmember 23 will again be pivotally moved clockwise, closing the passage19, thereby causing the pressure in chamber 11 to increase and againactuate the remote pneumatic component connected to the tube 14. Thespring washer 18 permits adjustment of the noZZle 17 with reference tothe under side of the cooperating horizontal portion of the controllingmember 23, to permit calibration of the air switch and to assure thatthe passage 19 is properly closed ofif when the air switch is inactuated position.

From the description of operation set out above, it will be evidentthat, because of the slight leftward positioning of pivot pin 21 inrelation to the mouth of nozzle passage 19, the resultant of the weightsof the legs 26 and 27 will act to close the nozzle passage. This forcewill be opposed by the force provided by the jet effect on leg 27 of theorifice 32 and the pressure at the mouth of passage 19. The orifice 32is so sized with relation to the pressure in chamber 11 that thisre-setting force total is always larger than the force exerted by theresultant moment provided by the weight of the legs 26 and 27 about pin21, so that, when de-actuated, the member 23 will be moved to open thepassage 19. This net force tending to open the passage 19 must, ofcourse, be overcome by the magnetic actuator 31 to shift the air switchto closed position.

In Fig. 3 there is disclosed an air switch having the same components asthe air switch referred to with reference to Fig. 1 but modified so asto provide a normally closed device. This-modification is performed byrotating the control body through an angle of 180 from its position ofFig. 1, so that the re-setting orifice 32 is positioned adjacent the leg26 of the controlling member. Under these conditions the air issuingfrom the orifice 32 acts against the leg 26 and the permeable member 29becomes the actuating means which is attracted by the magnet 31. Asviewed in Fig. 3, the air switch is shown in de-actuated position withthe controlling member 23 having been re-set by the force exertedthereon at orifice 32, aided by the resultant moment of the weight ofmember 23 about pin 21. Under these conditions the passage H is closedand the external pneumatic component connected to the tube 14 ispressurized. When the magnet 31 is brought into proximity with thepermeable member 29, as indicated in broken lines in Fig. 3, theattractive force exerted on the member 29 will move the controllingmember 23 into its broken line position. Passage 19 will thereupon beuncovered, permitting the pressure within the chamber 11 to rapidlydecrease, thereby depressurizing the external pneumatic component. Whenthe magnet 31 is displaced from attracting relation to the permeablemember 29, the force exerted at the re-setting orifice 32 upon the leg26 will again re-set the controlling member into its solid line positionof Fig. '1, thereby again pressurizing the external pneumatic componentconnected to the tube 14.

In the normally closed type of device described above, the resultantmoment about pin 21 exerted by the weight of member 23 will tend toclose the passage 19. With the air switch deactuated, orifice 32 must beso sized with relation to the pressure in the chamber 11 that the forceexerted by its jet effect on leg 26 together with the force exerted bythe weight of member 23 will be sufiicient to re-set the switch againstthe force exerted on the member 23 by the pressure existing at the mouthof the nozzle passage 19. This net force tending to close the passage 19will, of course, be the force which must be overcome by the magneticactuator 31 to open the switch.

Referring now to Fig. 4 there is disclosed a modified form of permeablemember 28 which is indicated at 28a. In this form, the permeable member28a is elongated horizontally and is adapted to cooperate with anactuating magnet, such as magnet 31 in Fig. 1, which is moved laterallywith respect to the air switch housing. From a comparison of Figs. 1 and4, it will be apparent that the actuating magnet will hold the leg 26 inattracted position during the interval in which the magnet moveslaterally along the face of the permeable member 28a. Thus, lengtheningor shortening the lateral extension of the member 28a provides aconvenient means for fixing the magnitude of the positional displacementof the magnet required to actuate and de-actuate the air switch.

A further modified form' of the permeable member 28 is shown at 28b inFig. 5. Here the member 28b is elongated vertically and is adapted tocooperate with a controlling magnet, such as magnet 31 of Fig. 1, which,in its controlling movement, moves Vertically along the leg 25. From theprevious discussion in regard to Fig. 4 it will be evident that themagnitude of the vertical motion of the controlling magnet required toactuate and de-actuate the air switch; in other words the operatingdifferential thereof, may be conveniently varied by proper sizing of thevertical dimension of the member 23b.

From the foregoing it will be apparent that the present inventionprovides an air switch which may be readily modified into either anormally open or a normally closed air switch, and in which a re-settingorifice is provided to'positively reset the switch when it isde-actuated.

Modifications of the present invention may occur to those skilled in theart, however, the scope of the invention is to be limited only by theappended claims.

I claim:

1. A pneumatic control comprising an elongated body having an inlet andan outlet communicating with a pressure chamber within the body, meansproviding a control orifice at one endface'of the body, said orificeproviding communication between the pressure chamber and atmosphere,magnetically actuated closure means for said orifice comprising aU-shaped controlling member having a central portion overlying saidorifice for cooperation therewith, pivotal mounting means for thecontrolling member carried by said body adjacent said orifice, the-legsof said controlling member being coextensive with said body on oppositesides thereof, means for magnetically coupling-one'of said legs to anexternal magnetic operator comprising a permeable armature membercarried by said one of' said legs at its free extremity, and a resetorifice communicating with said body inlet and extending through asidewall of said housing adjacent the other of said legs, said resetorifice being thereby adapted to provide a re setting force against saidother leg for opposing said external magnetic operator.

2. An assembly as claimed in claim 1 in which the armature membercooperates with a vertically movable magnetic operator and extends overa part of the length of said one leg to thereby increase the operatingdifferential of the control an amount depending on the magnitude of saidextending part.

3. An assembly'as claimed in claim 1 in which the armature membercooperates with a horizontally movable magnetic operator and extends adistance laterally beyond the longitudinal axis of said one leg tothereby increase the operating difierential of the control an amountdepending'on the magnitude of said extending distance.

4. A pneumatic control comprising an elongated body having an inlet andan outlet communicating with a pressure chamber within the body, acontrol orifice at one endface of the body communicating with thepressure chamber, magnetically actuated closure means for saidorificecomprising a U-shaped controlling member having a central portionoverlying said orifice for cooperation therewith, pivotal mounting meansfor the controlling member adjacent said control orifice, the legs ofsaid controlling member being substantially co-extensive with said body,means for magnetically coupling one of said legs to an external magneticoperator, a reset orifice communicating with said body inlet andextending through a sidewall of said housing adjacent the other one ofsaid legs, said reset orifice being thereby adapted to provide are-setting force against said other leg for opposing said externalmagnetic operator.

5. A pneumatic control comprising an elongated body having an inlet andan outlet communicating with a pressure chamber within the body, acontrol orifice at one endface of the body communicating with thepressure chamber, magnetically actuated closure means for said resetorifice comprising a U-shaped controlling member 5 having a centralportion overlying said orifice for cooperation therewith, pivotalmounting means for the controlling member adjacent said orifice, thelegs of said controlling member being co-extensive with said body,

means for magnetically coupling one of said legs to an 10 externalmagnetic operator comprising a permeable armature member carried by saidone of said legs, a re-set orifice communicating with said body inletand extending through a sidewall of said housing adjacent the other ofsaid legs, said orifice being thereby adapted to provide a re-settingforce against said other leg for opposing said external magneticoperator.

No references cited.

